1. Field of the Invention
The present invention relates to an actuator and a vehicle steering device.
2. Description of the Related Art
Four-wheel vehicles in recent years often include a vehicle steering device for rear wheels in order to control a steering angle of the rear wheels to a desired angle according to a traveling state.
As the vehicle steering device, there are a left-right integrated type for integrally steering left and right wheels with one actuator and a left-right independent type for providing actuators on the left and right side, respectively, and steering the left and right wheels independently from each other.
The actuator used in the vehicle steering device of the left-right independent type includes, in general, a telescopic rod, a motor including a rotating shaft, a worm gear and a worm wheel that reduce rotating speed of the rotating shaft, and a converting device (a ball screw or a feed screw) that converts a rotary motion of the worm wheel into a linear motion of the rod and advances and retracts the rod (see Japanese Patent Application Laid-open No. 2009-243621 (Patent Literature 1)). The actuator changes a projection amount of the rod to control steering angles of the wheels.
Incidentally, in some case, the wheels receive a load from a road surface during traveling of the vehicle and external force is input in the axial direction of the rod. When the external force is transmitted to the converting device, the worm wheel, the worm gear, and the motor, it is likely that the strength of the components is deteriorated and the projection amount of the rod changes.
Because of such circumstance, in Japanese Patent Application Laid-open No. 2003-237614 (Patent Literature 2) and Japanese Patent Application Laid-open No. 2003-81106 (Patent Literature 3), a reverse input preventing device is provided on a transmission route of driving force of the motor to prevent the input external force from being transmitted to the motor side.
Note that the reverse input preventing device includes an input member connected to components on an input side on the transmission route of the driving force and an output member connected to components on an output side.
Patent Literature 1: Japanese Patent Application Laid-open No. 2009-243621
Patent Literature 2: Japanese Patent Application Laid-open No. 2003-237614
Patent Literature 3: Japanese Patent Application Laid-open No. 2003-81106
However, when the reverse input preventing device is provided in the actuator as in the related art, the number of components such as ball bearings for rotatably supporting the input member and the output member increases.